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debian-mirror-gitlab/doc/administration/auth/ldap.md
Sruthi Chandran 0329642ba5 New upstream version 11.8.0
2019-03-02 22:35:43 +05:30

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LDAP

GitLab integrates with LDAP to support user authentication. This integration works with most LDAP-compliant directory servers, including Microsoft Active Directory, Apple Open Directory, Open LDAP, and 389 Server. GitLab Enterprise Editions include enhanced integration, including group membership syncing as well as multiple LDAP servers support.

GitLab EE

The information on this page is relevant for both GitLab CE and EE. For more details about EE-specific LDAP features, see the LDAP Enterprise Edition documentation.

Security

GitLab assumes that LDAP users are not able to change their LDAP 'mail', 'email' or 'userPrincipalName' attribute. An LDAP user who is allowed to change their email on the LDAP server can potentially take over any account on your GitLab server.

We recommend against using LDAP integration if your LDAP users are allowed to change their 'mail', 'email' or 'userPrincipalName' attribute on the LDAP server.

User deletion

If a user is deleted from the LDAP server, they will be blocked in GitLab, as well. Users will be immediately blocked from logging in. However, there is an LDAP check cache time (sync time) of one hour (see note). This means users that are already logged in or are using Git over SSH will still be able to access GitLab for up to one hour. Manually block the user in the GitLab Admin area to immediately block all access.

NOTE: Note: GitLab Enterprise Edition Starter supports a configurable sync time, with a default of one hour.

Git password authentication

LDAP-enabled users can always authenticate with Git using their GitLab username or email and LDAP password, even if password authentication for Git is disabled in the application settings.

Configuration

NOTE: Note: In GitLab Enterprise Edition Starter, you can configure multiple LDAP servers to connect to one GitLab server.

For a complete guide on configuring LDAP with GitLab Community Edition, please check the admin guide How to configure LDAP with GitLab CE.

To enable LDAP integration you need to add your LDAP server settings in /etc/gitlab/gitlab.rb or /home/git/gitlab/config/gitlab.yml for Omnibus GitLab and installations from source respectively.

There is a Rake task to check LDAP configuration. After configuring LDAP using the documentation below, see LDAP check Rake task for information on the LDAP check Rake task.

Prior to version 7.4, GitLab used a different syntax for configuring LDAP integration. The old LDAP integration syntax still works but may be removed in a future version. If your gitlab.rb or gitlab.yml file contains LDAP settings in both the old syntax and the new syntax, only the old syntax will be used by GitLab.

The configuration inside gitlab_rails['ldap_servers'] below is sensitive to incorrect indentation. Be sure to retain the indentation given in the example. Copy/paste can sometimes cause problems.

NOTE: Note: The encryption value ssl corresponds to 'Simple TLS' in the LDAP library. tls corresponds to StartTLS, not to be confused with regular TLS. Normally, if you specify ssl it will be on port 636, while tls (StartTLS) would be on port 389. plain also operates on port 389.

Omnibus configuration

gitlab_rails['ldap_enabled'] = true
gitlab_rails['ldap_servers'] = YAML.load <<-EOS # remember to close this block with 'EOS' below
##
## 'main' is the GitLab 'provider ID' of this LDAP server
##
main:
  ##
  ## A human-friendly name for your LDAP server. It is OK to change the label later,
  ## for instance if you find out it is too large to fit on the web page.
  ##
  ## Example: 'Paris' or 'Acme, Ltd.'
  ##
  label: 'LDAP'

  ##
  ## Example: 'ldap.mydomain.com'
  ##
  host: '_your_ldap_server'

  ##
  ## This port is an example, it is sometimes different but it is always an
  ## integer and not a string.
  ##
  port: 389 # usually 636 for SSL
  uid: 'sAMAccountName' # This should be the attribute, not the value that maps to uid.

  ##
  ## Examples: 'america\momo' or 'CN=Gitlab Git,CN=Users,DC=mydomain,DC=com'
  ##
  bind_dn: '_the_full_dn_of_the_user_you_will_bind_with'
  password: '_the_password_of_the_bind_user'

  ##
  ## Encryption method. The "method" key is deprecated in favor of
  ## "encryption".
  ##
  ##   Examples: "start_tls" or "simple_tls" or "plain"
  ##
  ##   Deprecated values: "tls" was replaced with "start_tls" and "ssl" was
  ##   replaced with "simple_tls".
  ##
  ##
  encryption: 'plain'

  ##
  ## Enables SSL certificate verification if encryption method is
  ## "start_tls" or "simple_tls". Defaults to true since GitLab 10.0 for
  ## security. This may break installations upon upgrade to 10.0, that did
  ## not know their LDAP SSL certificates were not set up properly.
  ##
  verify_certificates: true

  ##
  ## Specifies the SSL version for OpenSSL to use, if the OpenSSL default
  ## is not appropriate.
  ##
  ##   Example: 'TLSv1_1'
  ##
  ##
  ssl_version: ''

  ##
  ## Set a timeout, in seconds, for LDAP queries. This helps avoid blocking
  ## a request if the LDAP server becomes unresponsive.
  ## A value of 0 means there is no timeout.
  ##
  timeout: 10

  ##
  ## This setting specifies if LDAP server is Active Directory LDAP server.
  ## For non AD servers it skips the AD specific queries.
  ## If your LDAP server is not AD, set this to false.
  ##
  active_directory: true

  ##
  ## If allow_username_or_email_login is enabled, GitLab will ignore everything
  ## after the first '@' in the LDAP username submitted by the user on login.
  ##
  ## Example:
  ## - the user enters 'jane.doe@example.com' and 'p@ssw0rd' as LDAP credentials;
  ## - GitLab queries the LDAP server with 'jane.doe' and 'p@ssw0rd'.
  ##
  ## If you are using "uid: 'userPrincipalName'" on ActiveDirectory you need to
  ## disable this setting, because the userPrincipalName contains an '@'.
  ##
  allow_username_or_email_login: false

  ##
  ## To maintain tight control over the number of active users on your GitLab installation,
  ## enable this setting to keep new users blocked until they have been cleared by the admin
  ## (default: false).
  ##
  block_auto_created_users: false

  ##
  ## Base where we can search for users
  ##
  ##   Ex. 'ou=People,dc=gitlab,dc=example' or 'DC=mydomain,DC=com'
  ##
  ##
  base: ''

  ##
  ## Filter LDAP users
  ##
  ##   Format: RFC 4515 https://tools.ietf.org/search/rfc4515
  ##   Ex. (employeeType=developer)
  ##
  ##   Note: GitLab does not support omniauth-ldap's custom filter syntax.
  ##
  ##   Example for getting only specific users:
  ##   '(&(objectclass=user)(|(samaccountname=momo)(samaccountname=toto)))'
  ##
  user_filter: ''

  ##
  ## LDAP attributes that GitLab will use to create an account for the LDAP user.
  ## The specified attribute can either be the attribute name as a string (e.g. 'mail'),
  ## or an array of attribute names to try in order (e.g. ['mail', 'email']).
  ## Note that the user's LDAP login will always be the attribute specified as `uid` above.
  ##
  attributes:
    ##
    ## The username will be used in paths for the user's own projects
    ## (like `gitlab.example.com/username/project`) and when mentioning
    ## them in issues, merge request and comments (like `@username`).
    ## If the attribute specified for `username` contains an email address,
    ## the GitLab username will be the part of the email address before the '@'.
    ##
    username: ['uid', 'userid', 'sAMAccountName']
    email:    ['mail', 'email', 'userPrincipalName']

    ##
    ## If no full name could be found at the attribute specified for `name`,
    ## the full name is determined using the attributes specified for
    ## `first_name` and `last_name`.
    ##
    name:       'cn'
    first_name: 'givenName'
    last_name:  'sn'

  ##
  ## If lowercase_usernames is enabled, GitLab will lower case the username.
  ##
  lowercase_usernames: false

  ##
  ## EE only
  ##

  ## Base where we can search for groups
  ##
  ##   Ex. ou=groups,dc=gitlab,dc=example
  ##
  group_base: ''

  ## The CN of a group containing GitLab administrators
  ##
  ##   Ex. administrators
  ##
  ##   Note: Not `cn=administrators` or the full DN
  ##
  admin_group: ''

  ## An array of CNs of groups containing users that should be considered external
  ##
  ##   Ex. ['interns', 'contractors']
  ##
  ##   Note: Not `cn=interns` or the full DN
  ##
  external_groups: []

  ##
  ## The LDAP attribute containing a user's public SSH key
  ##
  ##   Example: sshPublicKey
  ##
  sync_ssh_keys: false

## GitLab EE only: add more LDAP servers
## Choose an ID made of a-z and 0-9 . This ID will be stored in the database
## so that GitLab can remember which LDAP server a user belongs to.
#uswest2:
#  label:
#  host:
#  ....
EOS

Source configuration

Use the same format as gitlab_rails['ldap_servers'] for the contents under servers: in the example below:

production:
  # snip...
  ldap:
    enabled: false
    servers:
      ##
      ## 'main' is the GitLab 'provider ID' of this LDAP server
      ##
      main:
        ##
        ## A human-friendly name for your LDAP server. It is OK to change the label later,
        ## for instance if you find out it is too large to fit on the web page.
        ##
        ## Example: 'Paris' or 'Acme, Ltd.'
        label: 'LDAP'
        ## snip...

Using an LDAP filter to limit access to your GitLab server

If you want to limit all GitLab access to a subset of the LDAP users on your LDAP server, the first step should be to narrow the configured base. However, it is sometimes necessary to filter users further. In this case, you can set up an LDAP user filter. The filter must comply with RFC 4515.

Omnibus configuration

gitlab_rails['ldap_servers'] = YAML.load <<-EOS
main:
  # snip...
  user_filter: '(employeeType=developer)'
EOS

Source configuration

production:
  ldap:
    servers:
      main:
        # snip...
        user_filter: '(employeeType=developer)'

Tip: If you want to limit access to the nested members of an Active Directory group, you can use the following syntax:

(memberOf:1.2.840.113556.1.4.1941:=CN=My Group,DC=Example,DC=com)

Find more information about this "LDAP_MATCHING_RULE_IN_CHAIN" filter at https://docs.microsoft.com/en-us/windows/desktop/ADSI/search-filter-syntax. Support for nested members in the user filter should not be confused with group sync nested groups support (EE only).

Please note that GitLab does not support the custom filter syntax used by omniauth-ldap.

Escaping special characters

If the user_filter DN contains special characters. For example, a comma:

OU=GitLab, Inc,DC=gitlab,DC=com

This character needs to be escaped as documented in RFC 4515.

Due to the way the string is parsed, the special character needs to be converted to hex and \\5C\\ (5C = \ in hex) added before it. As an example the above DN would look like

OU=GitLab\\5C\\2C Inc,DC=gitlab,DC=com

Enabling LDAP sign-in for existing GitLab users

When a user signs in to GitLab with LDAP for the first time, and their LDAP email address is the primary email address of an existing GitLab user, then the LDAP DN will be associated with the existing user. If the LDAP email attribute is not found in GitLab's database, a new user is created.

In other words, if an existing GitLab user wants to enable LDAP sign-in for themselves, they should check that their GitLab email address matches their LDAP email address, and then sign into GitLab via their LDAP credentials.

Enabling LDAP username lowercase

Some LDAP servers, depending on their configurations, can return uppercase usernames. This can lead to several confusing issues like, for example, creating links or namespaces with uppercase names.

GitLab can automatically lowercase usernames provided by the LDAP server by enabling the configuration option lowercase_usernames. By default, this configuration option is false.

Omnibus configuration

  1. Edit /etc/gitlab/gitlab.rb:

    gitlab_rails['ldap_servers'] = YAML.load <<-EOS
main:
  # snip...
  lowercase_usernames: true
EOS

  2. Reconfigure GitLab for the changes to take effect.

Source configuration

  1. Edit config/gitlab.yaml:

    production:
  ldap:
    servers:
      main:
        # snip...
        lowercase_usernames: true

  2. Restart GitLab for the changes to take effect.

Encryption

TLS Server Authentication

There are two encryption methods, simple_tls and start_tls.

For either encryption method, if setting verify_certificates: false, TLS encryption is established with the LDAP server before any LDAP-protocol data is exchanged but no validation of the LDAP server's SSL certificate is performed.

Note

: Before GitLab 9.5, verify_certificates: false is the default if unspecified.

Limitations

TLS Client Authentication

Not implemented by Net::LDAP. You should disable anonymous LDAP authentication and enable simple or SASL authentication. The TLS client authentication setting in your LDAP server cannot be mandatory and clients cannot be authenticated with the TLS protocol.

Troubleshooting

Debug LDAP user filter with ldapsearch

This example uses ldapsearch and assumes you are using ActiveDirectory. The following query returns the login names of the users that will be allowed to log in to GitLab if you configure your own user_filter.

ldapsearch -H ldaps://$host:$port -D "$bind_dn" -y bind_dn_password.txt  -b "$base" "$user_filter" sAMAccountName
  • Variables beginning with a $ refer to a variable from the LDAP section of your configuration file.
  • Replace ldaps:// with ldap:// if you are using the plain authentication method. Port 389 is the default ldap:// port and 636 is the default ldaps:// port.
  • We are assuming the password for the bind_dn user is in bind_dn_password.txt.

Invalid credentials when logging in

  • Make sure the user you are binding with has enough permissions to read the user's tree and traverse it.

  • Check that the user_filter is not blocking otherwise valid users.

  • Run the following check command to make sure that the LDAP settings are correct and GitLab can see your users:

    # For Omnibus installations
sudo gitlab-rake gitlab:ldap:check

# For installations from source
sudo -u git -H bundle exec rake gitlab:ldap:check RAILS_ENV=production

Connection Refused

If you are getting 'Connection Refused' errors when trying to connect to the LDAP server please double-check the LDAP port and encryption settings used by GitLab. Common combinations are encryption: 'plain' and port: 389, OR encryption: 'simple_tls' and port: 636.

Troubleshooting

If a user account is blocked or unblocked due to the LDAP configuration, a message will be logged to application.log.

If there is an unexpected error during an LDAP lookup (configuration error, timeout), the login is rejected and a message will be logged to production.log.